1. Field of the Invention
The present invention relates to a discharging system for discharging a smoothing capacitor connected in parallel to a switching circuit.
2. Description of the Related Art
Japanese patent Application Laid-open No. 10-248263 discloses an electric automobile provided with a motor/generator as a traveling drive source. In this electric automobile, when charging a smoothing capacitor connected to an inverter for converting a DC current from a main battery into an AC current to drive the motor/generator, the voltage of the smoothing capacitor is reduced by a DC-DC converter and effectively utilized for charging of a battery for an auxiliary.
There is another conventional electric automobile in which an electric charge of a smoothing capacitor of an inverter is consumed by a discharging circuit provided with a discharging resistor, thereby discharging the smoothing capacitor.
The DC-DC converter does not function, when the voltage on its input side is reduced to a value equal to or lower than a lowest operable voltage. Therefore, there is a problem that the discharging of the smoothing capacitor is possible before the voltage of the smoothing capacitor reaches the lowest operable voltage, but the smoothing capacitor cannot be discharged until the voltage reaches zero.
Also, in this system in which the discharging of the smoothing capacitor is conducted using a special discharging circuit, the number of parts is disadvantageously increased by the discharging circuit to cause an increase in the cost.